Is Rising CO₂ Quietly Making Our Food Less Nutritious?

Is Rising CO₂ Quietly Making Our Food Less Nutritious?

Short answer: Yes, new research shows rising atmospheric carbon dioxide (CO₂) is reducing zinc, iron, and protein in dozens of staple crops, even as yields stay the same or grow. Here’s what dietitians need to know.

Climate change discussions within the nutrition field have traditionally focused on food availability, droughts, floods, and shifts in growing seasons. But there’s a quieter story emerging in the research: rising CO₂ may be changing the nutritional composition of the food itself, independent of weather or yield.

What Did the New Study Actually Find?

A recent study published in Global Change Biology compiled evidence from 109 published studies to create the largest analysis to date examining how rising atmospheric CO₂ affects crop nutrition. The analysis included more than 5,300 data entries spanning approximately 29,500 paired observations across 43 food crops and 32 nutrients.

Their conclusion: as CO₂ rises, most nutrients decline. Zinc took the biggest hit, averaging a few percentage points lower overall but reaching as high as a 37.5% reduction in chickpeas. Iron and protein (measured via nitrogen content) showed similar downward trends. On average, nutrient concentrations dropped 3-4% across crops, with some crop-nutrient pairs seeing losses over 30%.

Meanwhile, calorie content tends to rise under the same conditions so future crops may fill people up without adequately nourishing them.

Why Is This Happening?

Plants use CO₂ as a raw material for photosynthesis. More CO₂ generally means faster growth and more carbohydrate production, but mineral and protein uptake from the soil doesn’t scale up to match. The result is a kind of dilution: bigger, faster-growing plants with proportionally fewer nutrients packed in.

The researchers found nutrient declines across a wide variety of commonly consumed crops, including wheat, rice, soybeans, legumes, and some vegetables, suggesting that the effects are widespread rather than limited to a few plant species.

Why Should Dietitians Care About This?

This isn’t a distant, hypothetical concern. It intersects with problems dietitians already manage every day:

• Zinc and iron gaps are already common in the U.S. population, particularly among older adults, pregnant women, and those on plant-forward diets.
• “Hidden hunger” (adequate calories, inadequate micronutrients) becomes harder to catch when staple foods look nutritionally unchanged on the surface but quietly deliver less.
• Dietary guidance built on current food composition data may drift out of date as crop nutrient profiles shift over the coming decades.

Who’s Most Vulnerable?

• Older adults, who already face reduced nutrient absorption and appetite
• Pregnant and lactating individuals with elevated iron and zinc needs
• Infants and children in critical growth windows
• Populations relying heavily on staple grains (rice, wheat) with limited dietary diversity
• Predominantly plant-based eaters who depend on legumes and grains for iron and zinc

What Can Dietitians Do With This Information?

You can’t change atmospheric chemistry, but you can adjust how you counsel and advocate:

• Emphasize dietary diversity over reliance on any single staple crop for key nutrients
• Reinforce zinc and iron-rich food sources such as legumes, nuts, seeds, and animal proteins where appropriate, and fortified foods – especially for higher-risk populations
• Watch for updates to food composition databases, which may eventually reflect these shifts
• Bring this into patient and client education as one more reason variety and nutrient density matter, rather than focusing just on calorie counts
• Stay current – this is an active and fast-evolving area of research

The Bottom Line

Nutrient adequacy has always depended on what people eat. Emerging evidence suggests it may increasingly depend on how the food itself is changing, even before it reaches the plate. Dietitians who understand this shift are better positioned to counsel proactively rather than reactively as the research develops.

Frequently Asked Questions

Does rising CO₂ make food less nutritious? Yes. A 2025 meta-analysis of 43 crops found that higher atmospheric CO₂ is linked to declines in zinc, iron, and protein, even when crop yields hold steady or increase.

Which nutrients are most affected by elevated CO₂? Zinc shows the most consistent and largest declines (up to 37.5% in some crops like chickpeas) followed by measurable drops in iron and protein/nitrogen.

What is “hidden hunger”? Hidden hunger refers to consuming enough calories while falling short on essential nutrients. As some crops become less nutrient-dense under rising CO₂ levels, experts are concerned this form of malnutrition could become more common.

Why does this matter for dietitians specifically? It’s a forward-looking factor in nutrient adequacy counseling, food security planning, and public health advocacy – one more reason to emphasize dietary diversity and nutrient-dense food sources with clients and patients.

Curious how food systems and environmental shifts connect to the nutrition care you provide every day? Two CPE courses go deeper on this topic:

• The New Planetary Health Diet: The Science of Sustainable Eating (10.75 CPEUs, including 1 Health Equity CPEU) explores how global food systems intersect with environmental boundaries, health, and nutrition security.
• Plate to Planet: Impact of Food Choices on the Planet (8 CPEUs) examines how everyday food choices affect both personal health and planetary health.

Explore these and more at BeckyDorner.com to stay ahead of the research shaping dietetics practice.

Reference:

ter Haar, S.F., van Bodegom, P.M., Scherer, L.  (2025). CO₂ Rise Directly Impairs Crop Nutritional Quality. Global Change Biology, 31:e70568. https://doi.org/10.1111/gcb.70568